---
id: 64dc985e6720a23edac63b51
title: ステップ 17
challengeType: 20
dashedName: step-17
---

# --description--

The allowed disk movements between the rods exhibit a repetitive pattern occurring every three moves. For example, movements between rod `A` and rod `C` are allowed on the first, the fourth and the seventh move, where the remainder of the division between the move number and 3 is equal to 1.

Inside the previously created `for` loop, replace the existing `print()` call with an `if` statement that is triggered when `(i + 1) % 3 == 1`. Within this `if` statement, print `f'Move {i + 1} allowed between {source} and {target}'` using an f-string. Please, note that `i + 1` is the move number since `i` is zero during the first iteration.

# --hints--

You should have an `if` statement that should be executed when `(i + 1) % 3 == 1`.

```js
({test: () => assert.match(code, /if\s+\(\s*i\s*\+\s*1\s*\)\s*%\s*3\s*==\s*1\s*:/)})
```

You should print the string `f'Move {i + 1} allowed between {source} and {target}'` using an f-string.

```js
({test: () => assert.match(code, /print\s*\(\s*f('|")Move\s\{\s*i\s*\+\s*1\s*\}\sallowed\sbetween\s\{\s*source\s*\}\sand\s\{\s*target\s*\s*\}\1\s*\)/)})
```

# --seed--

## --seed-contents--

```py
NUMBER_OF_DISKS = 3
number_of_moves = 2**NUMBER_OF_DISKS - 1
rods = {
    'A': list(range(NUMBER_OF_DISKS, 0, -1)),
    'B': [],
    'C': []
}

--fcc-editable-region--
def move(n, source, auxiliary, target):
    # display starting configuration
    print(rods)
    for i in range(number_of_moves):
        print(i)
--fcc-editable-region--

# initiate call from source A to target C with auxiliary B
move(NUMBER_OF_DISKS, 'A', 'B', 'C')
```
